Recording apparatus for radiotelegraphic signals



A. E. BLONDEL.

TUS FOR RADIO'TELEGRAPHIC SIGNALS.

RECORDING APPAHA APPLICATION FILED APR.26, 191 1,400,517'. Pfl-tema 1190.26, 1921..

.iE-gi Erg. j. Fil?. 3.

Ewen-6W: @uw gemma/,- yer UNITED STATES .PATENT OFFICE.

ANDRE EUG-NE BLONDEL, 0F PARIS, FRANCE. p

RECORDING APVP'ALRAT'US FIOR RADIOTELEGRAPHIG SIG-NALS.

To all whom it may concern? Be it known that I7 ANDR E. BLONDEL, a citizen of the Republic of France, residing at 41 Avenue de la Bourdonnais, Paris, in the Republic of France, have invented certain new and useful Improvements in Recording Apparatus for` Radiotele raphic Signals, (for which I have iiled app ication inv France, April 4, 1918,) of which the following is a specification.

In French Patent No. 451614, of the 9th `December, 1912, and in the various additions thereto, the use is'indicated of galvanometers or oscillographs of resonance having a variable characteristic period, which are adjusted to resonance with alternating v'currents of any frequency, by` varying the tension in the Wires of the biiilarsuspension.`

It was also indicated, in-the said main French patent, in paragraph 4, that this apparatus could beutilized for the purpose of effecting the selection of radio-'telegraphic Waves, either by creating for the 'latter'a certain periodic rhythm by producing 'them by means of alternators or by means of apparatus giving a musical discharge or else by producing, in the circuit for the reception of sustained waves, beats the frequency of which can be adjusted by meanszof a ticker or similar apparatus.

Into this latter category there enter, and

will naturally enter, .all kinds of beat-producing devices, and in particular those that are nowadays designated. by the name of' heterodynes, with all known `or possible arrangements of the connections; since it is' sufficient, as indicatedA in the said main French Patent No. 451614, to substitute the resonance" oscillograph for the telephone employed inall arrangements investigated for the reception of sound.

In the reports of the Academie des Sciences for the first half of the year 1914,

page 1645, I described an arrangement in which the oscillograph is in circuit with one or more condensers and a self-induction coil forming a resonance circuit. In a patent of addition (No. 19736) to the said French Patent No. 451614, the diagram of Figure l shows an arrangement with condensers and an inductance a, I) capable of being excited by induction. In the circuit a, b, G, containing the resonance oscillograph the constants may be adjusted by varying the selfinduction a, b, or the capacities 1, C2. If

Specification ofLettcrs Patent.y

Patented Dec.` 20, 1921.

Application filedy April 26, 1919. Serial No. 293,003.

this adjustment is effected in such-a Way that be obtained than by electrical resonance alone or by mechanical resonance alone; especially if care is taken that the electro# mechanical damping of the vibrating member (by the currentsthat it induces) is less than the mechanical damping.

VMoreover, as soon as one departs very far from resonance the coeiicient of reduction of amplitudeof the oscillations of frequencies loweror higher than the frequency to which both the electric circuit and the vibrating equipment are tuned, is approximately equal to the product of the coeliicients of reduction relative respectively to each of these members alone.

Forthe applica-tion of simple mechanical resonance to reception by wireless telegraphy, all the methods at present in use for the reception of musical waves or for the detection of sustained waves by means of apparatus operating upon the heterod ne beat system are very simply applica le, since all that is necessaryis to substitute for the telephone the vibrating galvanometer or oscillograph, and to bring the latter to the desired resonance frequency by varying the tension in the suspenslon wires or their disosclllotance part. Bilar-suspension graphs, with or without a small frame stuck on to the bifilar (or on to a flat spring servingv the same purpose) give, according to the length of the suspension, and according tothe tension, a whole scale of frequencies, which may go from a few hundreds of vibrations per second for frame apparatus, up to several thousands per second for apparatus withoutv frames.

In order to bring about the double resonance, all that is necessary is to employ arrangements in which the telephone circuit is branched, not directly on to the plate circuit of the detector member (when lamps 'and lheterodynes areemployed), but on to a Zcircuit of low resistance coupled vthrough capacity .or through induction with the detection circuit, in such a Way as to reduce ,the damping. of the electrical oscillations, `Which isproduced by thegresistaiicefin circuit. Ify the coupling is made lthroughl a transformer one has every facility for giving the ,windings of the latter the most favorable constants. l l l If thecoupling takes place by induction, a condenser is added in series. If the coupling takes Iplace by condenser, a self-induction is added in series. In all cases the capacity and inductance of the circuit are' 'regulated in such a. Way as to realize the constood by reference to the accompanying drawing in which i v Figures 1, 2 and 3 are diagrams of alternative arrangements of circuits embodying the invention While Figs. 1', 2 and 3 are slight variations of each respectively.

In Figs. 1 to 3, A is the aerial, E is the earth, D represents the detecting apparatus and in a general Way the group of apparatus which may be added to it (z'. e., high and lovv frequency amplifiers, etc.) and H represents a heterodyne source. arranged in any Way in the vicinity of the receiving apparatus.

From the receiving box proceeds a circuit 'C-R--L of loW resistance traversed by the detected current. On'the other hand a tuned galvanometer G, to which are added a resistance R', and inductanceL, and a condenser C (these three accessories being adjust-able) is put in relation with the circuit of the detected current either by connection to 'the ends of the condenser C (connection by capacity) see Fig. 1 or by connection to the ends of the inductance L (inductive connection) see Fig. 2, or by a transformer L-S (see Fig. 3). In thecase of Fig. 1 the condensers C'and C may be combined and the diagram shown in Fig. 1' will be obtained. In like manner in the case of 2 and 3 I may combine the inductance of the circuit of dctection (see Fig. 2') or with the secondary winding of the transformer (see Fig. 3').

The adjustment of the apparatus consi-sts in. obtaining, `by successive adjustments on the one hand the tuning of the mechanical movement, and on the other hand the tuning of the electric circuit containing the galvanometer to the frequency of the beats to be recorded.

justment 'is eiiected by variation of the'inductance L' and of the capacity C' (together K or separately) the variation of the resistance R' permitting of the adjustment of the electromeclianical damping (before referred to) to a suitable value. The critical value Will generally be chosen. The adjustment which is thus definite permits ofobtaining the maximum of amplitude of the oscillations in the minimum of time. The -apparatus is thus rendered capable of recording radioteletelegraphic signals transmitted at great speed. Such is the new industrial result achieved by the invention.

What I claim and desire to secure by Letters Patent of the United States is 1. Recording apparatus for radiotelegraphic signals comprising in combination a detector receiving the action of the aerial, an electric circuit of low resistance connected to the detector, a vibrating galvanometer, an electrically tuned circuit comprising the galvanometer connected to the said circuit oflowy resistance, the frequency of the galvanometer itself being adjusted so that each symbol recorded comprises a sufficient number of oscillations sufficiently close together andthe electrical damping being, on the other hand, regulated so that tlie tuning may be attained at the end of a very small number of oscillations.

2. Recording apparatus for radiotelegraphic signals comprising in combination a lamp detector receiving the action of the aerial and a lieterodyne, an electric circuit of low resistance connected to the detector, a vibrating device comprising a suspension oscillograph provided with several Wires the length, tension and dam-ping of which are adjustable, an electric circuit electrically ltuned comprising the vibrating device `connected to the said circuit of low resistance,

corded comprises a sufiicient number of os cillations suficiently close together and the damping being on the other hand regulated so that the tuning may be attained at the end of a very small number of oscillations.

In testimony'whereof I afiix my signature in presence of two Witnesses.

ANDR EUGENE BLNDEL.

1Witnesses EUGENE Fiisrniiiiv, JOHN F. SiMoivs.

inductance the vibrating device being' 'itself adjusted so that each` character re- 

